In recent years, food life has become rich in variety. With regard to sweeteners added to foods, too, it has become required to satisfy various factors such as low sweetness, refreshing sweetness, low viscosity, water retention and heat resistance. Of these, as for the low sweetness, an attempt to achieve it by, e.g., merely adding sugar to food and drink in a smaller quantity results in a low-bodied taste, and hence relatively high-molecular weight starch sugars such as dextrin of various types have been used in order to lower the sweetness while keeping a saccharide concentration. In addition thereto, in recent years, various oligosaccharides have been put into use.
However, as stated above, what is needed for sweeteners is not merely a low sweetness but also various factors such as a well-bodied taste, a flavorfullness and harmony with other seasoning materials, and hence the sweeteners can not meet all these requirements. Thus, it is sought to further provide a new sweetener.
As one of the above oligosaccharides, nigerooligosaccharide has began to attract notice. As a process for producing this nigerooligosaccharide, the following process is known in the art.
For example, M. Stacey and J. M. Webber, Methods in Carbohydrate Chemistry, I, pp.339-341, Academic press 1962, discloses a proposal on a process in which nigeran, erucinan or the like, which is a polysaccharide produced by microorganisms, is used as a substrate and hydrolysis is carried out using an enzyme or an acid to produce the nigerooligosaccharide.
A process is also known in which the transglycosylation and/or condensation reaction of known .alpha.-glucosidase is utilized to produce nigerose (see Ken-ichi Kaneda et al., The Society of Japan Agricultural Chemistry, 53, pp.385-390, 1979; H. Fujimoto et al., Agric. Biol. Chem., 52, pp.1345-1351, 1988; etc.)
Japanese Patent Application Laid-open No. 3-22958 also discloses a process in which a cyclodextrin glucanotransferase is allowed to act on a starch hydrolyzate to produce nigerose.
Japanese Patent Application Laid-open No. 7-59559 still also discloses a process in which at least one of glycosyltransferases that provide .alpha.-1,3-linkage is allowed to act on a substrate containing an .alpha.-1,4-glucoside-linked polysaccharide or oligosaccharide, to produce the nigerooligosaccharide.
However, the process disclosed in M. Stacey and J. M. Webber, Methods in Carbohydrate Chemistry, I, pp.339-341, Academic press 1962, requires nigeran, erucinan or the like, which is so much expensive that it is not preferable as a process for enabling industrial and inexpensive mass production.
The process making use of .alpha.-glucosidase can only produce the nigerooligosaccharide in a very small quantity.
The process disclosed in Japanese Patent Application Laid-open No. 3-22958 requires the cyclodextrin glucanotransferase in a quantity 50 times or more than usual, and also is known to produce the nigerooligosaccharide in a small quantity (see Shoichi Kobayashi et al., Food Industries, 31, pp.20-29, 1988).
The process disclosed in Japanese Patent Application Laid-open No. 7-59559 can only produce the nigerooligosaccharide in an amount of 26.1% by weight per saccharide solid content, as so disclosed in Examples described in the publication, which is not a sufficient yield.
Thus, none of the conventional processes have achieved the mass production of nigerooligosaccharide in an industrial scale and inexpensively, and have been sought to be further improved so that the products can be used as sweeteners of food and drink.
Various dextrins and various oligosaccharides which are used partly in place of sugar in order to achieve a low sweetness while keeping a well-bodied taste have been unsatisfactory in view of quality of sweetness and physical properties such as heat resistance, acid resistance, moisture retention and low coloring properties and also in respect of the requirement for lower calorie.
The present invention was made taking account of the above problems. Accordingly, an object of the present invention is to provide a process for producing a starch sugar composition, which can mass-produce nigerooligosaccharide or its reduction products in an industrial scale and inexpensively; a starch sugar composition having the quality of a low sweetness and good sweetness and superior physical properties; and food and drink containing such a starch sugar composition.